A 0.236 mm $^{2}$ , 3.99 mW Fully Integrated 90 nm CMOS L1/L5 GPS Frequency Synthesizer Using a Regulated Ring VCO

A broad-band frequency synthesizer for L1/L5 dual-band GPS RF receiver is designed using a four-stage differential ring voltage controlled oscillator (VCO) with an on-chip regulator to compensate for variation by supply and temperature. Also, a pole-zero scalable loop filter is proposed to tune the loop bandwidth while keeping damping factor against wide variations of VCO gain. The proposed frequency synthesizer fabricated on a 90 nm CMOS process occupies 0.236 mm² and consumes 3.99 mW at 1.2 V. The measured phase noise is less than -85 dBc/Hz for all bands.